Apparatus and technique for incinerating solid fuels containing carbonizable material

ABSTRACT

A furnace is provided having preliminary and post incineration chambers in which the atmosphere is adapted for combustion of the fuel therein. The fuel is introduced into the post incineration chamber through the preliminary incineration chamber, while the atmosphere within the chambers is pressurized. In addition, a portion of the atmosphere is purged from the post incineration chamber, and discharged relatively outside of the furnace, while the whole of the atmosphere is purged from the preliminary incineration chamber, and discharged into the post incineration chamber.

United States Patent 1191 Lagen 1451 Dec. 11, 1973 APPARATUS AND TECHNIQUE FOR INCINERATING SOLID FUELS CONTAINING CARBONIZABLE MATERIAL [76] Inventor: William S. Lagen, 9931 Lake 7 Washington Blvd. NE, Bellevue, Wash. 98004 [22] Filed: July 31, 1972 [21] Appl. No.: 276,820

52 U.S.C1 ..110/8R,1l0/11,110/15 [51] Int. Cl. F23g 7/00 [58] Field of Search 110/7 R, 8 R, 11, 110/15, 18 R [56] References Cited UNITED STATES PATENTS 3,303,798 2/1967 Kartinen et a1. 110/11 3,697,256 10/1972 Engle 110/15 3,362,887 1/1968 Rodgers 110/11 X Primary Examinerl(enneth W. Sprague Attorney-Christensen, O'Connor, Garrison & l-Iavelka [57] ABSTRACT A furnace is provided having preliminary and post incineration chambers in which the atmosphere is adapted for combustion of the fuel therein. The fuel is introduced into the post incineration chamber through the preliminary incineration chamber, while the atmosphere within the chambers is pressurized. In addition, a portion of the atmosphere is purged from the post incineration chamber, and discharged relatively outside of the furnace, while the whole of the atmosphere is purged from the preliminary incineration chamber, and discharged into the post incineration chamber.

35 Claims, 11 Drawing Figures 50 /Z 4 za :4 52

PATENIED DEC 1 1 I975 SHEET 2 CF 3 APPARATUS AND TECHNIQUE FOR INCINERATING SOLID FUELS CONTAINING CARB ONIZABLE MATERIAL FIELD OF THE INVENTION This invention relates to an apparatus and technique for incinerating solid fuels such as sawdust and garbage which contain a carbonizable material, and in particular to an apparatus and technique of this nature which produces a relatively pollution free effluent.

SUMMARY OF THE INVENTION According to the invention, such an effluent can be produced by employing a furnace having preliminary and post incineration chambers in which the atmosphere is adapted for combustion of the fuel therein; by introducing the fuel into the post incineration chamber through the preliminary incineration chamber, while the atmosphere within the chambers is pressurized; and by purging a portion of the atmosphere from the post incineration chamber, and discharging it relatively outside of the furnace, while purging the whole of the atmosphere from the preliminary incineration chamber, and discharging the latter atmosphere into the post incineration chamber.

In this way, the unburned fuel will undergo preincineration, that is drying and precarbonization, in a chamber from which the whole of the atmoshphere is purged and subjected to an afterburning action; while only that fuel which has been preincinerated will be burned in the post incineration chamber, so that the atmosphere which is purged therefrom, will be the product of a carbonized fuel mass, and consequently, will be relatively pollution free.

The whole of the atmosphere in the post incineration chamber may be discharged outside of the furnace; or the balance of the atmosphere in the post incineration chamber may be discharged into the preliminary incineration chamber, to be purged and redelivered to the post incineration chamber, as indicated.

The atmosphere in the post incinerationchamber may be purged simply by flushing the same with a stream of pressurized air; or it may be purged by flushing it with a stream of pressurized air; while simultaneously drawing a vacuum on the chamber at a point opposite to the point at which the airstream is discharged into the same. Where the balance of the atmosphere in the post incineration chamber is discharged into the preliminary incineration chamber, to be purged and redelivered to the post incineration chamber, as indicated, the vacuum is drawn at a point in the preliminary incineration chamber opposite from that at which the balance of the atmosphere in the post incineration chamber, is discharged thereinto. Preferably, moreover, the airstream is intermixed with the atmosphere which is purged from the preliminary incineration chamber, before the latter atmosphere is redelivered to the post incineration chamber.

It is also preferred to discharge the atmosphere which is purged from the post incineration chamber, into a low pressure zone which subjects the same to a vortical motion to remove any suspended particles in the same before the atmosphere is discharged outside of the furnace.

In the presently preferred embodiments of the invention, the fuel is fed into the post incineration chamber through a chute which empties into the same through the preliminary incineration chamber. Meanwhile, the atmosphere in the preliminary incineration chamber is exhausted through the chute, there being an airlock device employed at the inlet to the chute, to assure that the atmosphere in the chute is unable to escape there through. The chute may approach the vertical, so that the fuel flows downwardly therethrough by gravity; or it may approach the horizontal, and the fuel may be fed therethrough by a power driven conveyor. Preferably, a stream of pressurized air is discharged across the inlet to the chute, so as to prevent the atmosphere in the chute from escaping therethrough. In fact, a portion of the atmosphere in the chute may be recirculated to the inlet, and discharged thereacross for this purpose.

BRIEF DESCRIPTION OF THE DRAWINGS These features will be better understood by reference to the accompanying drawings which illustrate certain of the presently preferred embodiments.

In the drawings, FIG. I is a vertical cross section of one embodiment;

FIG. 2 is a cross section along the line 22 thereof;

FIG. 3 is a cross section along the line 3-3 thereof;

FIG. 4 is a cross section along the line 4-4 thereof;

FIG. 5 is a part vertical cross section of a somewhat modified version;

FIGS. 6-8 are other such views of other modifications;

FIG. 9 is a still further modification;

FIG. W is a horizontal cross section of the same; and

FIG. llll is a vertical cross section of another embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, it will be seen that the apparatus in FIGS. I4 comprises an upright cylindrical furnace 2 which has an opening 4 in the top thereof through which the fuel 5 is introduced into the furnace from a conveyor 6 that discharges thereabove. Inside of the furnace, the fuel settles progressively downward, passing firstly, downward through an upright cylindrical chute 8 in which it is dried and preheated, and then into and downward toward the bottom of an open-top, refractory incinerator If) that is also cylindrical in shape, and chamfered and rabbeted at the top to accommodate the chute in upright telescopic engagement thereon. After the fuel enters the incinerator, it undergoes burning in the presence of a stream of pressurized air which is discharged into the incinerator through a central opening I2 in the bottom thereof. The airstream not only contributes air to the burning process, but in addition operates to purge the atmosphere from the incinerator in a manner to be explained.

As the air is discharged into the incinerator, it impinges against a truncated conical lid 14 which is mounted above the opening 112 to splay the air into a horizontal or laterally deflected flow pattern therearound. The air then escapes in part up through the length of the furnace, while another part escapes through a series of circumferential openings 16 in the bottom portion of the incinerator. The openings are defined by a corresponding series of angularly deflected vanes 18 which are set within a circumferential slot 20 extending about the wall of the incinerator. Beyond the openings, the air rises up through a moat-like trough 22 which is formed about the incinerator by an obliquely canted, but cylindrically rimmed, refractory parapet 24 erected therearound. However, due to the angular deflection of the vanes, and the conical section of the parapet, the air undergoes a vortical or cyclone motion in the trough, which tends to trap any particles that escape with the air. Otherwise, the air escapes through a flue 26 interposed between the left-hand side of the furnace, and the rim 24 of the parapet.

Meanwhile, the air rising up through the interior of the furnace, carries the heat of the incinerator into the chute 8, and assists in preheating the fuel before escaping through the top opening 4 of the furnace. Beyond the top opening, the air does not escape from the apparatus itself, however; but to the contrary is exhausted into a downwardly directed duct 28 that is interconnected between the opening 4 and the suction side of a blower 30 disposed at the right-hand side of the furnace. The blower also operates to supply pressurized air to the bottom opening 12 of the furnace, and for this purpose, intakes fresh air through an inlet 32 on the suction side thereof, and then intermixes the air with the atmosphere in the duct 28, before discharging the mixture into another duct 34 on the discharge side thereof.

In addition, the blower delivers air to an upwardly directed duct 36 which is associated with an airlock device 38 formed in the top opening 4 of the furnace. The airlock device includes a convergent-divergent nozzle 40 which is vertically arranged within the opening 4, and surrounded at the top by an annular manifold 42 which discharges the air in the duct 36, downwardly into the nozzle 40 about the rim thereof. At the mouth of the nozzle, the air meets the upcoming air in the furnace, and is swept into an annular clearance 44 between the nozzle and the rim of the opening 4, where it is exhausted into the duct 28, through an intermediate manifold 46 associated with the duct 28 about the waist of the nozzle.

Alternatively, the duct 36 may be fed by a separate blower indicated in imaginary lines at 48.

To initiate the burning process, liquid or gaseous fuel is fed to one or more burners (not shown) in the lid 14, there being a valve controlled fuel line 50 for this purpose in the support for the lid. The burners may also be used to augment the burning process, where the fuel is exceptionally wet.

Dampers 52 are also employed in the ducts 28, 34, and 36, and in the flue 26, to control the airflow therethrough.

In lieu of the airlock device 38 employed in FIGS. 1-4, a mechanical airlock device may be employed,

such as the conventional device seen at 54 in FIG. 5.

Also, if desired, the fuel may be dumped into the furnace through a side opening in the chute, such as that seen at 56 in the chute 8' of FIG. 6, which side opening 56 is again jacketed (at 58), however, to provide a counter flow of air which is exhausted with the gases and fumes through the top opening 4 of the furnace.

Likewise, it is not necessary to discharge the airstream into the incinerator through an opening in the bottom thereof; but to the contrary, as in FIG. 7, the air may be discharged into the incinerator through a jacketed side opening 60, and thence allowed to escape into a flue 61, through a grate 62 in the bottom of the incinerator.

In FIG. 8, the bottom portion of the incinerator 10" is surrounded by an annular jacket 64, in which the air undergoes a vortical motion, after exiting through a circumferential slot 66, preceded by a grate 68 of relatively angularly oriented vanes that are interposed between the lid 14 and the slot, on the bottom of the incinerator. Moreover, the air then leaves the jacket through a boiler or heat exchanger 70, although for the sake of controlling the heat exchanger input, without affecting the operation of the apparatus otherwise, there is a flue 72 interconnected with the passage 74 to the heat exchanger, through which any excess air may be discharged from the system.

In FIGS. 9 and 10 the fresh air is taken in through a damper controlled passage 76 which is disposed opposite the incinerator 10", on a radius thereof, and has a shoe 78 about the mouth thereof, which is only slightly offset from the incinerator, so that the air is preheated as it is drawn in between the shoe and the incinerator. The apparatus is also equipped with heat exchanger 80 in the discharge jacket 82 about the bottom portion of the incinerator, and the exchanger and jacket are eccentric to the incinerator, so as to augment the heat exchange effect. The effluent leaves through a flue passage 84, after being purged from the incinerator by an airstream which is introduced through the bottom of the incinerator against a grate 86.

In FIGS. 1-10, the fuel 5 undergoes gravity flow through the chute 8 and into the incinerator 10, where it is converted first to a carbonized condition in the upper preliminary incineration levels 5 of the incinerator, and then consumed completely in the lower post incineration pit 5" of the same. On the other hand, in FIG. 11, the fuel is dumped into a refractory pit 88 from a power-driven conveyor 90 which passes through a refractory chute 92 on the left-hand side of the furnace 94. In the chute, the fuel undergoes preheating and carbonization on the conveyor, in the presence of a crosscurrent of fresh air from a plenum 96 therebelow. The air is supplied by a blower 98, and is exhaustedthrough a return duct 100 served by a blower 102. The latter blower discharges in turn into a duct 103, which exits into the pit 88 through a V-shaped grate 104 in the bottom thereof.

A series of manifold-connected burners 106 are employed to initiate the burning process on the conveyor, and/or to augment the process where needed. By the time the fuel is discharged from the conveyor, through an opening 108 at the right-hand end of the chute, the residue is thoroughly dried and precarbonized; so that as a consequence, the effluent leaving the pit through the flue 112 thereabove, is relatively pollution free.

An intake 110 enables the blower 102 to intermix fresh air with the return flow in the duct 100.

What is claimed is:

l. A method of incinerating a solid fuel containing carbonizable material, in a furnace having a preliminary incineration chamber with an intake therein and a post incineration chamber with a fuel retainer therein, comprising feeding the fuel onto the fuel retainer along a line passing through the preliminary incineration chamber from the intake, pressurizing the atmosphere in the chambers with an oxygen containing gas while purging the whole of the atmosphere from the preliminary incineration chamber and discharging the same into the post incineration chamber, and opening the post incineration chamber to the outside of the furnace at a point adjacent to the fuel retainer while closing the atmosphere in the post and preliminary incineration chambers to the outside of the furnace between the fuel retainer and the intake along the line of feed, so that a portion of the atmosphere in the post incineration chamber is discharged to the outside of the furnace from the region in which the fuel is collected on the retainer.

2. The method according to claim 1 wherein the whole of the atmosphere in the post incineration chamber is exhausted outside of the furnace.

3. The method according to claim 1 wherein the balance of the atmosphere in the post incineration chamber is discharged into the preliminary incineration chamber, to be purged and redelivered to the post incineration chamber, as indicated.

4. The method according to claim 1 wherein the atmosphere in the chambers is pressurized by supplying the same with a stream of pressurized air.

5. The method according to claim 1 wherein the post incineration chamber is opened to the outside of the furnace at a point above the fuel retainer, and the fuel is fed onto the retainer along a line sidewise therefrom.

6. The method according to claim 1 wherein the post incineration chamber is opened to the outside of the furnace at a point below the fuel retainer, and the fuel is fed onto the retainer along a line upright therefrom.

7. The method according to claim 1 wherein the post incineration chamber is opened to the outside of the furnace at a point sidewise of the fuel retainer, and the fuel is fed onto the retainer along a line upright therefrom.

8. A method of incinerating a solid fuel containing carbonizable material, comprising providing a furnace having preliminary and post incineration chambers in which the atmosphere is adapted for combustion of the fuel therein, introducing the fuel into the post incineration chamber through the preliminary incineration chamber, while pressurizing the atmosphere within the chambers; and purging a portion of the atmosphere from the post incineration chamber, and discharging it relatively outside of the furnace, while purging the whole of the atmosphere from the preliminary incineration chamber, and discharging the latter atmosphere into the post incineration chamber, the atmosphere in the post incineration chamber being purged by flushing the same with a stream of pressurized air, while simultaneously drawing a vaccuum on the chamber at a point opposite to the point at which the airstream is discharged into the same.

9. The method according to claim 8 wherein the balance of the atmosphere in the post incineration chamber is discharged into the preliminary incineration chamber, to be purged and redelivered to the post incineration chamber, as indicated, and the vacuum is drawn at a point in the preliminary incineration chamber opposite from that at which the balance of the atmosphere in the post incineration chamber, is discharged thereinto.

10. The method according to claim 9 wherein the airstream is intermixed with the atmosphere that is purged from the preliminary incineration chamber, before the latter atmosphere is redelivered to the post incineration chamber.

11. The method according to claim 1 wherein the atmosphere which is exhausted from the post incineration chamber, is, discharged into a low pressure zone which subjects the same to a vortical motion to remove any suspended particles in the same before the atmosphere is discharged outside of the furnace.

12. The method according to claim 1 wherein the fuel is fed into the post incineration chamber through a chute which empties into the same through the preliminary incineration chamber, and the atmosphere in the preliminary incineration chamber is exhausted through the chute, there being an airlock device employed at the inlet to the chute, to assure that the atmosphere in the chute is unable to escape therethrough.

13. The method according to claim 12 wherein the chute approaches the vertical so that the fuel flows downwardly therethrough by gravity.

14. The method according to claim 12 wherein the chute approaches the horizontal, and the fuel is fed therethrough by a power driven conveyor.

15. The method according to claim 12 wherein a stream of pressurized air is discharged across the inlet to the chute, so as to prevent the atmosphere in the chute from escaping therethrough.

16. The method according to claim 15 wherein a portion of the atmosphere in the chute is recirculated to the inlet, and discharged thereacross.

17. A method of incinerating a solid fuel containing carbonizable material, comprising providing a furnace having preliminary and post incineration chambers in which the atmosphere is adapted for combustion of the fuel therein, introducing the fuel into the post incineration chamber through the preliminary incineration chamber, while pressurizing the atmosphere within the chambers; and purging a portion of the atmosphere from the post incineration chamber, and discharging it relatively outside of the furnace, while purging the whole of the atmosphere from the preliminary incineration chamber, and discharging the latter atmosphere into the post incineration chamber, the fuel being fed into the post incineration chamber through a chute which empties into the same through the preliminary incineration chamber, and the atmosphere in the preliminary incineration chamber being exhausted through the chute, there being an airlock device at the inlet to the chute, operative to discharge a stream of pressurized air across the inlet, so as to prevent the atmosphere in the chute from escaping therethrough.

18. Apparatus for incinerating a solid fuel containing carbonizable material, comprising a furnace having a preliminary incineration chamber with an intake therein and a post incineration chamber with a fuel retainer therein, means for feeding the fuel onto the fuel retainer along a line passing through the preliminary incineration chamber from the intake, means for pressurizing the atmosphere in the chambers with an oxygen-containing gas while purging the whole of the atmosphere from the preliminary incineration chamber and discharging the same into the post incineration chamber, and means for opening the post incineration chamber to the outside of the furnace at a point adjacent to the fuel retainer while closing the atmosphere in the post and preliminary incineration chambers to the outside of the furnace between the fuel retainer and the intake along the line of feed, so that a portion of the atmosphere in the post incineration chamber is discharged to the outside of the furnace from the region in which the fuel is collected on the retainer.

19. The apparatus according to claim 18 wherein the post incineration chamber is open to the outside of the furnace at a point above the fuel retainer, and the preliminary incineration chamber is disposed so that the fuel is fed onto the retainer along a line sidewise therefrom.

20. The apparatus according to claim 18 wherein the post incineration chamber is open to the outside of the furnace at a point below the fuel retainer, and the preliminary incineration chamber is disposed so that the fuel is fed onto the retainer along a line upright therefrom.

21. The apparatus according to claim 18 wherein the post incineration chamber is open to the outside of the furnace at a point sidewise of the fuel retainer, and the preliminary incineration chamber is disposed so that the fuel is fed onto the retainer along a line upright therefrom.

22. The apparatus according to claim 18 wherein the last-named means is operative to discharge the whole of the atmosphere in the post incineration chamber outside of the furnace.

23. The apparatus according to claim 18 wherein the last-named means is operative to discharge the balance of the atmosphere in the post incineration chamber, into the preliminary incineration chamber, to be purged and redelivered to the post incineration chamber, as indicated.

24. The apparatus according to claim 18 wherein the pressurization means includes means for supplying the atmosphere in the chambers with a stream of pressurized air.

25. The apparatus according to claim 18 wherein the last-named means is operative to discharge the atmosphere which is exhausted from the post incineration chamber, into a low pressure zone which subjects the same to a vortical motion to remove any suspended particles in the same before the atmosphere is discharged outside of the furnace.

26. The apparatus according to claim 18 wherein the means for feeding the fuel into the post incineration chamber includes a chute which empties into the same through the preliminary incineration chamber, and the pressurization means is operative to purge the atmosphere in the preliminary incineration chamber through the chute, there being an airlock device at the inlet to the chute, to assure that the atmosphere in the chute is unable to escape therethrough.

27. The apparatus according to claim 26 wherein the chute approaches the vertical so that the fuel flows downwardly therethrough by gravity.

28. The apparatus according to claim 26 wherein the chute approaches the horizontal, and the means for feeding the fuel also includes a power driven conveyor for feeding the fuel through the chute.

29. The apparatus according to claim 26 wherein the airlock device includes means for discharging a stream of pressurized air across the inlet to the chute, so as to prevent the atmosphere in the chute from escaping therethrough.

30. The apparatus according to claim 29 wherein the air discharge means is operative to recirc'ulate a portion of the atmosphere in the chute to the inlet, and to discharge the portion thereacross.

31. The apparatus according to claim 18 further comprising means defining a heat exchange passage for the atmosphere which is exhausted from the post incin eration chamber.

32. An apparatus for incinerating a solid fuel containing carbonizable material, comprising a furnace having preliminary and post incineration chambers which provide an atmosphere for combustion of the fuel therein, means for introducing the fuel into the post incineration chamber through the preliminary incineration chamber, means for pressurizing the atmosphere within the chambers, and means for purging a portion of the atmosphere from the post incineration chamber, and discharging it relatively outside of the furnace, while purging the whole of the atmosphere from the preliminary incineration chamber, and discharging the latter atmosphere into the post incineration chamber, the purge means including means for flushing the atmosphere in the post incineration chamber with a stream of pressurized air, while simultaneously drawing a vacuum on the chamber at a point opposite to the point at which the airstream is discharged into the same.

33. The apparatus according to claim 32 wherein the purge means is operative to discharge the balance of the atmosphere in the post incineration chamber, into the preliminary incineration chamber, to be purged and redelivered to the post incineration chamber, as indicated, and the vacuum is drawn at a point in the preliminary incineration chamber opposite from that at which the balance of the atmosphere in the post incineration chamber, is discharged thereinto.

34. The apparatus according to claim 33 wherein the purge means is operative to intermix the airstream with the atmosphere that is purged from the preliminary incineration chamber, before the latter atmosphere is redilivered to the post incineration chamber.

35. An apparatus for incinerating a solid fuel containing carbonizable material, comprising a furnace having preliminary and post incineration chambers which provide an atmosphere for combustion of the fuel therein, means for introducing the fuel into the post incineration chamber through the preliminary incineration chamber, means for pressurizing the atmosphere within the chambers, and means for purging a portion of the atmosphere from the post incineration chamber, and discharging it relatively outside of the furnace, while purging the whole of the atmosphere from the preliminary incineration chamber, and discharging the latter atmosphere into the post incineration chamber, the means for introducing the fuel into the post incineration chamber including a chute which empties into the same through the preliminary incineration chamber, and the purge means being operative to exhaust the atmosphere in the preliminary incineration chamber through the chute, there being the airlock device at the inlet to the chute, operative to discharge a stream of pressurized air across the inlet, so as to prevent the atmosphere in the chute from escaping therethrough. 

1. A method of incinerating a solid fuel containing carbonizable material, in a furnace having a preliminary incineration chamber with an intake therein and a post incineration chamber with a fuel retainer therein, comprising feeding the fuel onto the fuel retainer along a line passing through the preliminary incineration chamber from the intake, pressurizing the atmosphere in the chambers with an oxygen containing gas while purging the whole of the atmosphere from the preliminary incineration chamber and discharging the same into the post incineration chamber, and opening the post incineration chamber to the outside of the furnace at a point adjacent to the fuel retainer while closing the atmosphere in the post and preliminary incineration chambers to the outside of the furnace between the fuel retainer and the intake along the line of feed, so that a portion of the atmosphere in the post incineration chamber is discharged to the outside of the furnace from the region in which the fuel is collected on the retainer.
 2. The method according to claim 1 wherein the whole of the atmosphere in the post incineration chamber is exhausted outside of the furnace.
 3. The method according to claim 1 wherein the balance of the atmosphere in the post incineration chamber is discharged into the preliminary incineration chamber, to be purged and redelivered to the post incineration chamber, as indicated.
 4. The method according to claim 1 wherein the atmosphere in the chambers is pressurized by supplying the same with a stream of pressurized air.
 5. The method according to claim 1 wherein the post incineration chamber is opened to the outside of the furnace at a point above the fuel retainer, and the fuel is fed onto the retainer along a line sidewise therefrom.
 6. The method according to claim 1 wherein the post incineration chamber is opened to the outside of the furnace at a point below the fuel retainer, and the fuel is fed onto the retainer along a line upright therefrom.
 7. The method according to claim 1 wherein the post incineration chamber is opened to the outside of the furnace at a point sidewise of the fuel retainer, and the fuel is fed onto the retainer along a line upright therefrom.
 8. A method of Incinerating a solid fuel containing carbonizable material, comprising providing a furnace having preliminary and post incineration chambers in which the atmosphere is adapted for combustion of the fuel therein, introducing the fuel into the post incineration chamber through the preliminary incineration chamber, while pressurizing the atmosphere within the chambers; and purging a portion of the atmosphere from the post incineration chamber, and discharging it relatively outside of the furnace, while purging the whole of the atmosphere from the preliminary incineration chamber, and discharging the latter atmosphere into the post incineration chamber, the atmosphere in the post incineration chamber being purged by flushing the same with a stream of pressurized air, while simultaneously drawing a vaccuum on the chamber at a point opposite to the point at which the airstream is discharged into the same.
 9. The method according to claim 8 wherein the balance of the atmosphere in the post incineration chamber is discharged into the preliminary incineration chamber, to be purged and redelivered to the post incineration chamber, as indicated, and the vacuum is drawn at a point in the preliminary incineration chamber opposite from that at which the balance of the atmosphere in the post incineration chamber, is discharged thereinto.
 10. The method according to claim 9 wherein the airstream is intermixed with the atmosphere that is purged from the preliminary incineration chamber, before the latter atmosphere is redelivered to the post incineration chamber.
 11. The method according to claim 1 wherein the atmosphere which is exhausted from the post incineration chamber, is discharged into a low pressure zone which subjects the same to a vortical motion to remove any suspended particles in the same before the atmosphere is discharged outside of the furnace.
 12. The method according to claim 1 wherein the fuel is fed into the post incineration chamber through a chute which empties into the same through the preliminary incineration chamber, and the atmosphere in the preliminary incineration chamber is exhausted through the chute, there being an airlock device employed at the inlet to the chute, to assure that the atmosphere in the chute is unable to escape therethrough.
 13. The method according to claim 12 wherein the chute approaches the vertical so that the fuel flows downwardly therethrough by gravity.
 14. The method according to claim 12 wherein the chute approaches the horizontal, and the fuel is fed therethrough by a power driven conveyor.
 15. The method according to claim 12 wherein a stream of pressurized air is discharged across the inlet to the chute, so as to prevent the atmosphere in the chute from escaping therethrough.
 16. The method according to claim 15 wherein a portion of the atmosphere in the chute is recirculated to the inlet, and discharged thereacross.
 17. A method of incinerating a solid fuel containing carbonizable material, comprising providing a furnace having preliminary and post incineration chambers in which the atmosphere is adapted for combustion of the fuel therein, introducing the fuel into the post incineration chamber through the preliminary incineration chamber, while pressurizing the atmosphere within the chambers; and purging a portion of the atmosphere from the post incineration chamber, and discharging it relatively outside of the furnace, while purging the whole of the atmosphere from the preliminary incineration chamber, and discharging the latter atmosphere into the post incineration chamber, the fuel being fed into the post incineration chamber through a chute which empties into the same through the preliminary incineration chamber, and the atmosphere in the preliminary incineration chamber being exhausted through the chute, there being an airlock device at the inlet to the chute, operative to discharge a stream of pressurized air across the inlet, so as to prevent the atmosphere in the chute from escaping therethrough.
 18. Apparatus for incinerating a solid fuel containing carbonizable material, comprising a furnace having a preliminary incineration chamber with an intake therein and a post incineration chamber with a fuel retainer therein, means for feeding the fuel onto the fuel retainer along a line passing through the preliminary incineration chamber from the intake, means for pressurizing the atmosphere in the chambers with an oxygen-containing gas while purging the whole of the atmosphere from the preliminary incineration chamber and discharging the same into the post incineration chamber, and means for opening the post incineration chamber to the outside of the furnace at a point adjacent to the fuel retainer while closing the atmosphere in the post and preliminary incineration chambers to the outside of the furnace between the fuel retainer and the intake along the line of feed, so that a portion of the atmosphere in the post incineration chamber is discharged to the outside of the furnace from the region in which the fuel is collected on the retainer.
 19. The apparatus according to claim 18 wherein the post incineration chamber is open to the outside of the furnace at a point above the fuel retainer, and the preliminary incineration chamber is disposed so that the fuel is fed onto the retainer along a line sidewise therefrom.
 20. The apparatus according to claim 18 wherein the post incineration chamber is open to the outside of the furnace at a point below the fuel retainer, and the preliminary incineration chamber is disposed so that the fuel is fed onto the retainer along a line upright therefrom.
 21. The apparatus according to claim 18 wherein the post incineration chamber is open to the outside of the furnace at a point sidewise of the fuel retainer, and the preliminary incineration chamber is disposed so that the fuel is fed onto the retainer along a line upright therefrom.
 22. The apparatus according to claim 18 wherein the last-named means is operative to discharge the whole of the atmosphere in the post incineration chamber outside of the furnace.
 23. The apparatus according to claim 18 wherein the last-named means is operative to discharge the balance of the atmosphere in the post incineration chamber, into the preliminary incineration chamber, to be purged and redelivered to the post incineration chamber, as indicated.
 24. The apparatus according to claim 18 wherein the pressurization means includes means for supplying the atmosphere in the chambers with a stream of pressurized air.
 25. The apparatus according to claim 18 wherein the last-named means is operative to discharge the atmosphere which is exhausted from the post incineration chamber, into a low pressure zone which subjects the same to a vortical motion to remove any suspended particles in the same before the atmosphere is discharged outside of the furnace.
 26. The apparatus according to claim 18 wherein the means for feeding the fuel into the post incineration chamber includes a chute which empties into the same through the preliminary incineration chamber, and the pressurization means is operative to purge the atmosphere in the preliminary incineration chamber through the chute, there being an airlock device at the inlet to the chute, to assure that the atmosphere in the chute is unable to escape therethrough.
 27. The apparatus according to claim 26 wherein the chute approaches the vertical so that the fuel flows downwardly therethrough by gravity.
 28. The apparatus according to claim 26 wherein the chute approaches the horizontal, and the means for feeding the fuel also includes a power driven conveyor for feeding the fuel through the chute.
 29. The apparatus according to claim 26 wherein the airlock device includes means for discharging a stream of pressurized air across the inlet to the chute, so as to prevent the atmosphere in the chute from escaping therethrough.
 30. The apparatus according to claim 29 wherein the air discharge means is operative to recirculate a portion Of the atmosphere in the chute to the inlet, and to discharge the portion thereacross.
 31. The apparatus according to claim 18 further comprising means defining a heat exchange passage for the atmosphere which is exhausted from the post incineration chamber.
 32. An apparatus for incinerating a solid fuel containing carbonizable material, comprising a furnace having preliminary and post incineration chambers which provide an atmosphere for combustion of the fuel therein, means for introducing the fuel into the post incineration chamber through the preliminary incineration chamber, means for pressurizing the atmosphere within the chambers, and means for purging a portion of the atmosphere from the post incineration chamber, and discharging it relatively outside of the furnace, while purging the whole of the atmosphere from the preliminary incineration chamber, and discharging the latter atmosphere into the post incineration chamber, the purge means including means for flushing the atmosphere in the post incineration chamber with a stream of pressurized air, while simultaneously drawing a vacuum on the chamber at a point opposite to the point at which the airstream is discharged into the same.
 33. The apparatus according to claim 32 wherein the purge means is operative to discharge the balance of the atmosphere in the post incineration chamber, into the preliminary incineration chamber, to be purged and redelivered to the post incineration chamber, as indicated, and the vacuum is drawn at a point in the preliminary incineration chamber opposite from that at which the balance of the atmosphere in the post incineration chamber, is discharged thereinto.
 34. The apparatus according to claim 33 wherein the purge means is operative to intermix the airstream with the atmosphere that is purged from the preliminary incineration chamber, before the latter atmosphere is redilivered to the post incineration chamber.
 35. An apparatus for incinerating a solid fuel containing carbonizable material, comprising a furnace having preliminary and post incineration chambers which provide an atmosphere for combustion of the fuel therein, means for introducing the fuel into the post incineration chamber through the preliminary incineration chamber, means for pressurizing the atmosphere within the chambers, and means for purging a portion of the atmosphere from the post incineration chamber, and discharging it relatively outside of the furnace, while purging the whole of the atmosphere from the preliminary incineration chamber, and discharging the latter atmosphere into the post incineration chamber, the means for introducing the fuel into the post incineration chamber including a chute which empties into the same through the preliminary incineration chamber, and the purge means being operative to exhaust the atmosphere in the preliminary incineration chamber through the chute, there being the airlock device at the inlet to the chute, operative to discharge a stream of pressurized air across the inlet, so as to prevent the atmosphere in the chute from escaping therethrough. 